A limited slip differential in a vehicle typically employs a wet multi-plate clutch i.e., clutch plates are immersed in a lubricant. The limited slip differential typically has bevel gear or spur gear planetary systems which distribute the drive torque evenly to the two driving wheels irrespective of their rotational speed. This makes it possible for the driven wheels to roll during cornering without slip between the wheel and road surface in spite of their different rotational speed. In order for the slip to be controlled lubricants containing compounds capable of improving friction performance, dispersants and sulphur- and/or phosphorus-containing extreme pressure agents may be used. Examples of lubricants of this type are disclosed in U.S. Pat. Nos. 5,547,586; 4,180,466; 3,825,495; and European Patent Application 0 399 764 A1.
Lubricants containing compounds suitable for (i) deposit control (U.S. Pat. No. 3,284,409), and (ii) wear performance are described in International Application WO 96/037585, US Patent Application 2002/0119895, and U.S. Pat. No. 5,487,838.
U.S. Pat. No. 5,487,838 discloses a reaction product of a boron compound and a phospholipid. The reaction product may be used in a number of lubricants including an automatic transmission fluid, a gear oil, or a tractor fluid.
U.S. Pat. No. 5,135,669 discloses a lubricant composition containing a hydrogenated phospholipid (including hydrogenated lecithin, an antioxidant, a dispersant, a seal swell agent, an antiwear agent and a viscosity modifier. The hydrogenated phospholipid may also be reacted with a metal.
US Patent Application 2002/0119895 discloses (A) a molybdenum compound, and (B) a specific composition selected from (i) at least one borated overbased metal salt of acidic organic compounds, (ii) a combination of (a) at least one organic polysulfide or at least one ashless dithiocarbamate containing composition, and (b) at least one of metal thiophosphate, phosphate, P-containing compound of carboxylate, ester, ether or amide, borated dispersant, alkali metal borate, borated fatty amine, borated phospholipid, and their mixtures, and (iii) a combination of (i) and (ii). The lubricant composition is used to lubricate transmission and differential gears.
International Application WO 96/037585 discloses lubricant compositions containing (A) an antiwear improving amount of at least one molybdenum containing composition, and (B) at least one member selected from the group consisting of (i) at least one borated overbased metal salt of an acidic organic compound, provided that (A) and (Bi) are not the same, (ii) a combination of (a) at least one organic polysulfide or at least one ashless dithiocarbamate containing composition and (b) at least one component selected from the group consisting of a metal thiophosphate, a phosphoric acid ester or salt thereof, a phosphorus-containing carboxylic acid, ester, ether, or amide, a borated dispersant, an alkali metal borate, a borated fatty amine, a borated phospholipid, a borate ester, and mixtures thereof, and (iii) a combination of (i) and (ii). The lubricant includes 80W and 80W-90 gear oils.
U.S. Pat. No. 3,284,409 discloses an additive for hydrocarbon oils and lubricants containing a composition of component (A) a product obtained by the reaction of a succinic acid substituted by an aliphatic hydrocarbon with greater than 50 carbon atoms with greater than 0.5 equivalent of alkylene amine (ethylene amine (I), polyethylene polyamine) and with greater than 0.1 equivalent boron acids, their esters, or ammonium salts, or B2O3, and component (B) lipid phosphatides, such as lecithin. The lubricants may be useful for internal combustion engines, gear assemblies and power transmitting units. The example discloses use in an internal combustion engine.
U.S. Pat. No. 5,135,669 discloses hydrogenated, phospholipid compounds suitable as friction modifying materials that are employed in automatic transmission fluids.